Process for manufacturing safety fuses



Mmh 31, mm .1: FRITZSQHE mwmz:

PROCESS FOR MANUFACTURING SAFETY FUSES Filed Feb. 25, 1927 INVE NTOR JOHANNES F'RETZSCHE 5y izzis aZEarvzqys Fi v MM Patented Mar. 31, 1931 J'OHANNES FRITZSCHE, OF WIENER N EUSTADT, NEAR VIENNA, AUSTRIA PROCESS FOR MANUFACTURING SAFETY FUSES Application filed February 25, 1927, Serial No. 170,978, and in Germany February 25, 1926.

My invention relates to that class of safety fuses in which a core containing gun powder or a similar composition capable of burning without the access oftexternal air is provided with two layers of helically wound threads forming an inner wrapper. My invention consists of a process for manufacturing a safety fuse of thisclass in which the said inner wrapper is enclosed by an outer wrapper comprising at least one but preferably two or more layers of filaments, either threads or wires, successive layers of filaments being wound in opposite directions and open wound that is to say wound in such a manner that the adjacent filaments of each layer are separated from each other by a free interval of appreciable width say of a width 01 half the thickness of an individual filament.

In the drawings Figure l is a transverse section of a safety fuse constructed in accordance with the invention,

Fig. 2 is a longitudinal view of a fuse similar to that illustrated in Figure 1, but having an outer wrapper comprising two layers of filaments, various layers being cut away to show the construction more clearly.

Referring to the drawings there is a core 1, surrounded by an inner wrapper composed of two layers of filaments, 2 and 4, which are helically wound about the core 1 preferably in opposite directions. A protective layer 3 surroundsthe inner wrapper, and an outer wrapper is wound about the protective layer. In Figure 1, this outer wrapper is illustrated as comprising a single layer of filaments 5, while in Fig. 2 the outer layer comprises two oppositely wound filaments 5 and 5 The outer wrapper may be impregnated if desired by any known or convenient means. An outer coating 6, is applied to the outside of the outer wrapper, although the addition of this outer coating 6, is not always considered obligatory.

The object of this outer wrapper is to hold together reliably and in the proper position relatively to each other during manufacture the threads of the inner wrapper and to prevent them from being displaced in the further steps of the manufacture of the safety fuse such as reeling and unreeling, impregnating and others. I have found by close investigation that such displacements are very objectionable for the reason that they frequently cause sparking and even local bursting of the fuse, irregularity in burning and local developing of large amount of smoke. By providing an outer wrapper as above set forth also any tendency of the safety fuse to distort is etliciently counteracted during manufacture. In accordance with what has been said above, I find it possible to apply to the inner wrapper an outer wrapper immediately thereafter, that is to say without reeling and unreelmg the fuse between the application of such wrappers or so tol speak in one operation or in one and the same machine.

The outer wrapper may also be efficiently impregnated with any of the usual or pre ferred impregnating substances such as tar, pitch, hydrocarbons, asphaltum or the like solidifying at normal temperature applied to such outer wrapper in the usual way, say b passing the safety fuse already provided wit i the outer wrapper through a hopper or other suitable receptacle and a nozzle attached thereto, the hopper being filled with the impregnating substance. The latted then penetrates into the outer wrapper readily if the latter is open wound filling the intervals between the filaments of such outer wrapper. Thereby the entire safety fuse is strengthened and made impervious to moisture. The filaments of successive layers of the outer wrapper are wound in opposite directions, as will be seen by referring to Fig. 2.

In some cases'I may find it desirable to prevent the impregnating substance from reaching the core. In such cases I interpose between the outer wrapper and the core a protecting layer of some suitable material practically impervious to the impregnating substance such as paper or a finely pulverulent substance such as clay, lime, chalk or the like applied in a moistened state in any suitable or preferred manner. The protecting layer may be interposed between the outer and the inner wrapper or preferably between the two mu thread layers of the inner wrapper.

fected according to the invention by a suit-' able device mounted'in the machine between the apparatus for applying the inner and the outer wrapper. After applying the inner wrapper to the core, or with an open wound outer wrapper such testing might take place even after the outer wrapper has been applied to the inner wrapperin the same machine or separately.

What I claim is:

1. A process of manufacturing safety fuses consisting in applying to the core an. inner of a substance ractically impervious to the said impregnating substance.

6. A process for manufacturing safety fuses consisting in applying to the core an ,inner wrapper, testing the core provided with wrapper, testing the core provided with the inner wrapper and immediately thereafter applying to such inner wrapper an outer wrapper consisting of at least one layer of filaments helically wound on the inner wrapp 2. process of manufacturing safety fuses consisting in applying to the core an inner wrapper, testing the core provided with the inner wrapper and immediately thereafter applying to such inner wrapper an outer wrapper consisting of at least one layer of filaments helically open wound on the inner wrap er.

3. process of manufacturing safety fuses consisting in applying to the core an inner wrapper, testing the core provided with the inner wrapper and immediately thereafter applying to such inner wrapper an outer wrapper consisting of at least one layer of filaments open wound on the inner wrapper and in impregnating the said outer wrapper with a liquefied impregnating substance solidifying at normal temperature.

4. A process of manufacturing safety fuses consisting in appl ing to the core an inner wrapper, testing t e core provided with the inner wrapper and immediately thereafter applying to such inner wrapper an outer wrapper, consisting of at least two successive layers of filaments open wound on the inner wrapper and on each other, such sucessive layers being wound in opposite directions and in impregnating the said outer wrapper with a liquefied impregnating substance solidifying at normal temperature.

5. A process of manufacturing safety fuses consisting in applying to the core an inner wrapper, testing the core provided with the inner wrapper and applying a protective layer and immediately thereafter applying to such compound covering an outer wrapper consisting, of at least two successive layers of filaments open wound and in impregnating such outer wrapper with a liquefied impregnating substance solidifying at normal temperature, the said protective layer consisting 

